How to use depth_image_proc/register to convert a depth image from a tf to another?

Hello everybody!
I'm working on ROS Hydro on Ubuntu 12.04.
I have two simulated cameras: one depth camera and one RGB camera. They have a 4 cm horizontal offset between them, as specified on the urdf. I've successfully transformed the depth image into a point cloud using the depth_image_proc/point_cloud_xyzrgb nodelet as follows:

But to do this I cheated: I manually changed the scene_rgb_cam_wf frame_id to the scene_depth_cam_wf frame_id, something that is not true (as I said before, they have a horizontal displacement of 4 cm). I did it because otherwise I got this error:

So, by doing this I got my depth image transformed into a PoinCloudXYZRGB, but with the colors displaced. SO, to correct this I read that the depth_image_proc has another nodelet that lets you transform a depth image into the RGB image frame_id, the depth_image_proc/register.

So, I undid the manual change of the RGB image's frame id and wrote this .launch file: